concat columns to make one pandas code example

Example 1: concat 3 column in pandas

In[17]:df['combined']=df['bar'].astype(str)+'_'+df['foo']+'_'+df['new']

In[17]:df
Out[18]: 
   bar foo     new    combined
0    1   a   apple   1_a_apple
1    2   b  banana  2_b_banana
2    3   c    pear    3_c_pear

Example 2: how to concat on the basis of particular columns in pandas

In [6]: result = pd.concat(frames, keys=['x', 'y', 'z'])